Electrical high-voltage rotational machines, for example generators, comprise electrical conductors, a main insulation and a stator lamination stack. The main insulation has the function of durably insulating the electrical conductors electrically from one another, from the stator lamination stack and from the surroundings. During operation of the machines, electrical partial discharges which lead to formation of “treeing” channels in the main insulation occur. At the “treeing” channels, the main insulation can withstand only reduced electrical potentials and electrical breakdown of the main insulation can occur. A barrier against the partial discharges is achieved by use of an electrical insulation tape. The electrical insulation tape comprises an electrically insulation paper, for example a mica paper, which is applied to a support.
In the production of the main insulation, the electrical insulation tape is firstly wrapped around the conductor and then impregnated with a synthetic resin, for example an epoxy resin. The synthetic resin is subsequently cured. The use of nanosize and/or microsize inorganic particles which are added to the synthetic resin before impregnating and curing in order to improve the resistance of the main insulation is known.
To impregnate the electrical insulation tape, the conductor around which the electrical insulation tape has been wrapped is impregnated with the synthetic resin, for example in a tank in which the synthetic resin is present. Here, only a small proportion of the synthetic resin penetrates into the electrical insulation tape. The proportion of the synthetic resin remaining in the tank is returned to a stock vessel and kept in stock in order to be used at a later point in time for the production of further electrical insulation bodies. For this reason, the storage stability of the remaining synthetic resin is of great importance.